The present invention relates to a structure and method of preparing structures to serve as selective magnetic sorbents or bioplatforms and a method of using the sorbents in the removal of soluble materials such as, for example, lead, copper, or mercury cations or tungstate, uranyl, or cyanide anions from aqueous solutions. Specifically, the present invention relates to easily recoverable, microspheric magnetic structures comprising magnetic materials encapsulated in microporous shells produced through the gelling of a cellulose derivative. The structures can be filled with agents of choice.
Considerable interest exists in commercial and government facilities to develop a low cost, fully effective, recyclable means for total removal of toxic materials from waste water streams of all types, including agricultural run-off and geothermal brines. Similar interest exists in recovering strategic materials from natural brines and from industrial process streams.
The rate at which ion-exchange beads absorb or adsorb ions from dilute solution is directly proportional to the surface area of the beads and thus for a given weight of beads is inversely proportional to the size of the beads. Therefore, for a given weight of beads, increases in reaction rates can be achieved even at low concentration by raising the number and reducing the size of the beads. Conventional resins of small bead size are, however, very difficult to recover from process streams, especially when they become commingled with particulate waste matter. Since incorporation of one or more magnetic particles within small ion-exchange beads greatly increases the ease at which they can be recovered from process solutions, there have been many attempts to produce small, magnetic ion-exchange beads.
Chemically reactive magnetic microspheres have heretofore been constructed either through chemical surface treatment of solid magnetic dust or by the in-situ formation of small magnetic particles within gelled ion-exchange material. For example, magnetic particles have been encapsulated in a synthetic polymer onto which desirable functional groups for ion-exchange were grafted.
Mucopolysaccharides such as chitosan have been dissolved in acidified mixtures of iron chlorides. The addition of base causes the simultaneous formation of solid magnetite particles and the precipitation of the chitosan encapsulating the magnetic particles.
However, either economic or technical difficulties have prevented the widespread commercial application of magnetic ion-exchange structures. In practice, selectivity is very important to the economics of any ion-exchange process. This is especially true when the targeted species is dissolved in water rich in other ions. In general, the prior art has not been able to produce a structure with a magnetic core which has low cost, small size, and which can be tailored to be ion-specific to a variety of ions.